Chocolate Peanut Brittle

2 cups granulated sugar
1 cup light corn syrup
1/2 cup water
1 teaspoon salt
1 (6 ounce) package semisweet chocolate chips or 1 cup
2 tablespoons butter
1 teaspoon vanilla extract
1 1/2 cups salted peanuts

Combine sugar, syrup, water, and salt and boil to hard crack stage (300 degrees F) without stirring. Remove from heat and quickly stir in chocolate chips, butter, vanilla extract and peanuts. Pour quickly onto buttered cookie sheet. When cool, break into pieces.